This invention relates to insulation for water cooled pipes, and more specifically to insulation for reducing thermal energy losses in water cooled piping systems of a steel reheating furnace.
In steel mills, blooms, slabs, billets and bars must usually be reheated for a subsequent rolling or refinishing operation. The reheating is effected in a large refractory furnace along which the bodies to be reheated are advanced from an inlet end to an exit end along skid pipes across which they are transversely disposed. Because the temperature of the furnace must be on the order of 2400.degree. F. and the steel must be reheated uniformly throughout, the furnace must be of substantial length and high mechanical loads are placed on the supporting structure. To withstand these loads, a quite massive water cooled support system and large hollow pipes are used to provide the structural base for the skids. In order to prevent excessive loss of thermal energy within the furnace, horizontal and vertical parts of the piping are shielded by insulation.
In the prior art, rigid refractory insulation has extensively been used, but as noted in the patent to Boto et al., U.S. Pat. No. 3,820,947, the mechanical stresses and shocks within the skid system are transmitted to these preformed parts and cause unwanted fractures and destructive effects. It should also be noted that materials and labor costs for such installations are extremely high. In consequence, Boto el al propose the special construction in which an insulating blanket is disposed about the pipes, and held in place by a combination of threaded alloy studs projecting from the pipes, a refractory anchor held on the studs by a lock nut which is covered by a layer of high temperature mortar, and a rigidizing surface spray which penetrates substantially into the interior of the blanket. A number of other combinations of insulative blankets and rigid structures have been suggested, as evidenced by the patents to Greaney, U.S. Pat. No. 3,329,414 and Doherty et al., U.S. Pat. No. 3,486,533, but all suffer from substantial disadvantages in terms of the excessive amount of time required to install the structures, and the expense and difficulty of specially modifying the supporting structure.
In addition to the mechanical vibration and shock problems encountered in the furnace, insulative structures must be capable of withstanding falling and flying molten slag, which is continually being generated during furnace operation. In addition, the heat fluxes required are so high that substantial forces are generated by the impinging high velocity gases from the furnace jets. Accordingly, workers in the art have inherently considered that expensive high strength structures are required to meet these demanding conditions.